Process for shrinking non-woven webs

ABSTRACT

A process for the production of felts by shrinking a continuous random web of textile material which includes the steps of heating the material to be treated shock-like to a shrinking and heat-setting temperature and drawing a heated treatment medium through the web of material while it is being conveyed on a perforated surface of at least one sieve drum means, the differential pressure across the web of material on said surface being less than the shrinkage forces whereby a uniform shrinkage of the material is obtained.

United States Patent Fleissner 7 l*.]une 17, 1975 1 PROCESS FORSHRINKING NON-WOVEN 2,197,147 4/1940 Hadley 26/185 WEBS 2,908,06410/1959 Lauterbach et al. 28/72 NW X 3,272,898 9/1966 Knee 28/72 NW X[75] In entor: nz Fleiss g sb c e 3,374,646 3/1968 Fleissner 68/D1G. 5

Frankfurt am Main, Germany 3,460,898 8/1969 Fleissner..... 3,503,1353/1970 Fleissner 68/DIG. 5 [73] Asslgrleei VEPA AG, Swnzerland 3,529 4479/1970 Fleissner et al. 26/185 UX Notice: The portion of the term f i3,530,214 9/1970 Hermes 26/1815 X Eategt sulzis eql e 31, 19871 FOREIGNPATENTS OR APPLICATIONS as 942,930 11/1963 United Kingdom 11 34/115 [22]Filed: Jan. 24, 1973 1,004,909 9/1965 United Kingdom 34/115 [21] Appl'326559 Primary Examiner-Robert R. Mackey Related U.S. Application DataAttorney, Agent, or FirmCraig & Antonelli [63] Continuation of Ser. No.850,549, Aug. 5, 1969,

abwdoned- 57 ABSTRACT [30] Foreign Appncafion priority Dam A process forthe production of felts by shrinking a A 17 968 6 1785165 continuousrandom web of textile material which ineludes the steps of heating thematerial to be treated shock-like to a shrinking and heat-settingtemperature 5 ;62;itg bgggggbg and drawing a heated treatment mediumthrough the 28/72HR 72 NW web of material while it is being conveyed ona perfole 0 e 34/1 6'8"); rated surface of at least one sieve drummeans. the differential pressure across the web of material on saidsurface being less than the shrinkage forces whereby a [56] UNITE /:;:S:2ENTS uniform shrinkage of the material is obtained. 2.144.151 1/1939Hcinen 26118.5 10 Claims 6 Drawing Figures Mi /11111117 11 11 II I JUN]?9 PATENTEI] SHEET 1 3,889,325

5 Inventor:

MEI/42. FLEZSSNER- g W; M:

PATENTEDJUH 17 I975 Inventor:

HEINZ- FLEI5$NEK 4 7 fiwwf lq++ornay5 PROCESS FOR SHRINKING NON-WOVENWEBS '"CROSS REFERENCE TO RELATED APPLICATION This application is acontinuation of application Ser. No. 850,549, filed Aug. l5, 1969, nowabandoned.

BACKGROUND OF THE INVENTION The present invention relates to a processfor the production of felts, particularly synthetic leather, byshrinking a continusous random web which contains at least two fibertypes. Typical combinations of fiber I types include for example,polypropylene and a polyamide, polypropylene and rayon staple,polypropylene and a polyester, polyamide high-shrink fibers and normalpolyamide fibers, polyester high-shrink fibers and normal polyesterfibers, combinations of other synthetic fibers and the like. Accordingto the present process, one fiber of said combination of fibers shrinkssubstantially more under the influence of heat than the other one ofsaid combination of fibers. Advantageously, the continuous random web isneedled before shrinking.

It is well known to produce felts by shrinking wherein a certain portionhigh-shrink fibers are added to the felts. Shrinking is effected eitherin a water bowl or by jetting the web with hot air or, in the case of apolyamide, by treating said polyamide with steam. The well knownprocesses exhibit the disadvantages that the felts are corrugated afterthe shrinking process and accordingly optimum shrinkage values are notobtained.

SUMMARY OF THE INVENTION An object of the present invention is to avoidthe prior art disadvantages in processes for the production of felts.

Another object of the present invention is to provide an improvedprocess for the production of felts wherein the production of denser andsmoother felts is effected by means of shrinking.

Other objects and further scope of applicability of the presentinvention will become apparent from the detailed description givenhereinafter.

It should be understood, however, that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

Pursuant to the present invention, it has been found that theabovementioned disadvantages may be eliminated and a much improvedprocess for the production of felts may be obtained by heating acontinuous random web shock-like or rapidly to he shrinking and/rheat-setting temperature and by drawing a gaseous and/or vaporous orliquid treatment medium around and through the web of material, at leastduring a portion of the shrinking and/or heat-setting treatment stage,while it rests on a plane or a curved permeable support, such as forexample, a sieve drum means.

The conveying element may be a sieve subjected to a suction draft,advantageously one or more sieve drum =means. As a result of the suctiondraft the web or the felt is forced onto the sieve drum, and thus acompletely smooth felt is produced. Up to now, it was consideredimpossible to use conveying elements subjected to a suction draft forshrinking purposes in felt production because it was feared that thesuction draft would hold the web too firmly to the sieve and also thatshrinkage would not be uniform over the entire working width, that is,it was expected that the material would shrink more at the edge portionsthan in the middle portions of the material length. With the commontreatment devices with sieve drums subjected to a suction draft, thiseffect actually does occur. Here the suction draft is stronger than theshrinkage forces. However, in accordance with the present invention, ithas been found that a uniform shrinkage can be obtained using conveyingelements subjected to a suction draft, for example, sieve drum means, ifthe differential pressure used in producing the suction draft at the webis lower than about 40mm water column, preferably lower than about 20mmwater column. A particularly dense felt, as is required for syntheticleather is obtained if the material being treated is first penetrated bya treatment liquid at a temperature in excess of about C andsubsequently by a gaseous or vaporous treatment medium, for example, airwith a temperature of, for example, in excess of about C, for drying andrefixation. By said refixation, it is made sure that the other fibercomponent also shrinks. In case of polyester fibers, the refixationtemperature should be about 220C, whereas in the case polypropylenefibers a temperature of about 140C is sufficient for said refixation.

In order to achieve a shock-like shrinkage, if shrinkage is effected bymeans of a liquid, it is suggested to spray a cold treatment liquor, forexample, water, onto the web before the shrinking treatment. In thisway, a certain pre-shrinkage by the steam rising from the treatment bowlis avoided. Such a pre shrinkage is very detremental because the optimumshrinkage values cannot be reached with high-shrink fibers. It is wellknown that high-shrink fibers shrink an an amount up to about 50%.

Particularly with very wide material lengths of about 1.5m and more, itis advantageous if the web is exposed to the influence of the treatmentmedium before it is supported on the sieve means. Here it isparticularly desirable if the web is overfed in a wave-like mannerbefore it is deposited on the sieve means subjected to a suction draft,that is, generally a sieve drum means subjected to a suction draft. Anoverfeeding of the material in the lengthwise direction according to thedesired shrinkage values must, of course, be insured. Such an overfeedin width and an overfeed of the material in length can, for example, beachieved by means of a pair of rollers which are provided with annulargrooves and rings which are arranged in such a way that a ring of oneroller is situated above a recess of the other roller. By thedisplacement of the one roller against the other roller, the individualrings engage, more or less, with the recesses, that is, with the annulargrooves of the other roller and the needled web is thus passed into thetreatment medium atmosphere and/or passed to the conveying elementsubjected to a suction draft in a more or less corrugated condition. Theother surface of the rings should be bulged and/or have the shape of atorus in order to avoid marking the edge of the material.

After the webs are fully shrunk they are generally impregnated withbonding agents, for example, with synthetic latex, in order to obtain aleather-like structure. Another possibility of bonding the feltaccording to the present invention is to add melt fibers to thecontinuous random web of material and to effect bonding simultaneouslywith the shrinking and/or heat-setting treatment. If the felts are to beused for the production of synthetic leather, the bonded felts can besubsequently impregnated with a latex, if necessary. However, in manycases such a latex impregnation is no longer necessary. The felts can besubsequently coated or further processed in the usual way.

As an apparatus for carrying out the process according to the presentinvention, a device is suggested which comprises at least one sievemeans subjected to a suction draft, for example, at least one sieve drummeans subjected to a suction draft, which is provided with an inlet unitwhich permits the feeding and/or passage of the web of material with avariable overfeed (wave-like) in length and/or in width. Furthermore, avariable speed drive for establishing variations in the pump and/or fanspeeds, is to be correlated to the pump and/or the fan for theproduction of the suction draft.

It has been found that it is of particular advantage for treating thinwebs of material to use a sieve roller subjected to a preferably strongsuction draft as an inlet unit, since such a roller ensures anabsolutely uniform overfeed of the material over the entire workingwidth.

It is advantageous if the sieve drum heat-setting means is combined witha sieve drum bowl in which the web is freely guided in the treatmentliquor over a distance of at least cm, preferably about cm or more,before it is deposited on the sieve drum. Also, it is desirable to passthe web, with an overfeed in width (wave-like) into the treatmentliquor.

Instead of the synthetic fibers which have been mentioned above, anyother suitable synthetic fibers can, of course, be used for producingthe felts of the present invention. Suitable fibers include, forexample, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, andthe like.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become morefully understood from the detailed description given hereinbelow and theaccompanying drawings which are given by way of illustration and thusare not limitative of the present invention and wherein,

FIG. 1 is a longitudinal suction of a sieve drum apparatus according thepresent invention;

FIG. 2 is a longitudinal section of another sieve drum apparatusaccording to the present invention;

FIG. 3 is a longitudinal section of a combination of a sieve drum bowlwith a sieve drum heat-setting means;

FIG. 4 is a longitudinal section of still another sieve drum apparatusaccording to the present invention;

FIG. 5 is a cross sectional view of the aforementioned sieve drumapparatus, and;

FIG. 6 shows a pleating roller having rings to effect lateraloverfeeding of the textile material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,wherein like reference numerals are used throughout the various views todesignate like parts, the apparatus of the present invention comprises aheat-insulated housing 1 which is subdivided by a partitions means 2into a treatment chamber 3 and a fan chamber 4. In the treatment chamber3 sieve drums 5 for guiding the material are disposed as well as sievesheets 6 which are provided above and beneath the sieve drums 5. Thesieve sheets serve for equalizing the treatment medium flow. A fan 7 iscorrelated to at least one face of each sieve drum 5. This fan 7 drawsthe treatment medium out of the sieve drums and recirculates it backinto the treatment chamber 3 via heater batteries 8 so that a constantcirculation of the treatment medium is ensured. If the treatment mediumis air, some fresh air is generally drawn into the device at thedischarge end of the apparatus. An equal amount of the stale, moistureenriched air is discharged above the inlet of the apparatus.

In the apparatus according to FIGS. 1 and 2, a web 9 to be shrunk is fedto the first sieve drum 5 by means of conveyor belt 10 and roller 11. Inthe apparatus according to FIG. 1 the treatment medium is blown out ofthe first sieve drum. In this way an unrestricted shrinkage of the web 9is ensured. With the second sieve drum 5 the treatment medium flows fromthe outside to the inside of the sieve drum and thus the web 9 is heldto said sieve drum. At the same time, an ironing effect is obtained bythe suction draft. At the outlet of the apparatus according to FIG. 1 aconveyor belt 10 is again arranged. The device according to FIG. 2 isprovided with a roller 12 at the discharge end of the apparatus.

In the apparatus according to FIGv 2 the first sieve drum 5 is alsosubjected to a suction draft. Here, material shrinkage can be obtainedin an effective way by having the conveyor belt 10 and the roller 11rotate at a higher speed than the sieve drum 5, so that the web is fedwave-like to the sieve drum and allowed to shrink freely. By theutilization of a pair of rollers provided with rings and annular grooveswhich are staggered with respect to each other, it is possible to obtaina corresponding overfeed in the width.

In each sieve drum a stationary baffle 13 is provided at that side ofthe sieve drum which is not covered with the material being treated,said stationary baffle means interrupting the suction draft and/or theblowing effect at that side of the sieve drum means.

The apparatus according to FIG. 3 is of similar design as that of FIG. 2with the exception that at the inlet of the heat-setting chamber a pairof rollers 14 are arranged whereas at the outlet of said chamber a chute15 is arranged. To the heat-setting apparatus a bowl 16 with a sievedrum [7 subjected to a suction draft is correlated and a spray means 25is provided for spraying water onto the web 9 before the shrinkagetreatment. Also, in this case it is possible to overfeed the needled web9 to the sieve drum 17 by means of a pair of rollers 18. Subsequently,the web 9 which has been shrunk in the bowl is squeezed by means of asqueezer l9 and is dried and refixed on a subsequent sieve drumheatsetting means.

The apparatus according to FIG. 4 is of similar design as that accordingto FIG. 2 with the exception that the needled web 9 is passed to thefirst sieve drum 5 through a vertical duct 20. In this duct steam issprayed onto both sides of the material by means of jet tubes 21. Also,here it is advantageous if the pair of inlet rollers 14 is provided withrings and/or annular grooves in order to achieve a wave-like feeding ofthe materials and thus a more uniform shrinkage (as shown in FIG. 6).

As may be gathered from FIG. 5, adrum drive 22 is arranged at one sideof the housing and a fan drive 23 with a variable speed gear 24 isprovided at the other side of the housing.

The invention being thus described, it will be obvious that the same maybe varied in many way. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as will be apparent to one skilled in the art are intendedto be included.

What is claimed is:

1. A continuous process for the production of felts by shrinking acontinuous random web of textile material which comprises overfeeding aweb of textile material to a perforated surface of at least one sievedrum means subjected to a suction draft, conveying said web of textilematerial on said perforated surface, said web being retained on saidperforated surface only by said suction draft, heating the textilematerial to a shrinking temperature by drawing a heated treatment mediumthrough the web of material while the web is being conveyed on theperforated surface, the differential pressure across the web of materialon said perforated surface being lower than about 40 mm. water columnwhich is less than the shrinkage forces acting on said web of textilematerial whereby a uniform shrinkage of the web of material is obtainedon said perforated surface, and further heating the web of shrunktextile material on a perforated surface of at least one other sievedrum means subjected to a suction draft to effect heat-setting of saidtextile material while said web is in a smoothed-out condition.

2. The process of claim 1, wherein the differential pressure at the webof material is lower than about 20mm water column.

3. The process of claim 1, comprising overfeeding the web of material tothe surface of the first sieve drum longitudinally and laterally suchthat the width and the length of said web of material is conveyed onsaid sieve drum in a corrugated state.

4. The process of claim 1, wherein the continuous random web comprisesat least one synthetic fiber type selected from the group consisting ofpolyvinyl chloride, polyvinyl alcohol and polyacrylonitrile.

5. The process of claim 1, wherein steam is blown against both sides ofthe web of material before the material is placed on the perforatedsurface of the sieve drum means through which said treatment medium isdrawn to effect shrinkage of said material.

6. The process of claim 1, wherein the textile material consists of atleast two different types of fibers, one fiber type shrinkingsubstantially more under the influence of heat than the other.

7. The process of claim 1, wherein the web of textile material is firstpenetrated by a treatment liquid with a temperature greater than aboutC. to effect shrinkage of said material on said perforated surface ofsaid at least one sieve drum means and thereafter the web of material isheated by a gaseous treatment medium to a higher temperature for dryingand refixing of said material on the perforated surface of said at leastone other sieve drum means.

8. The process of claim 7, wherein the gaseous treatment medium isheated to a temperature ranging from to 220C.

9. The process of claim 7, wherein the web of material is sprayed withcold water before it is penetrated by the treatment liquid.

10. The process of claim 7, wherein the continuous random web comprisesat least two different fiber types selected from the group consisting ofpolypropylene and a polyamide, polypropylene and a rayon staple,polypropylene and a polyester, polyamide high-shrink fibers and normalpolyamide fibers, polyester highshrink fibers and normal polyesterfibers.

1. A continuous process for the production of felts by shrinking acontinuous random web of textile material which comprises overfeeding aweb of textile material to a perforated surface of at least one sievedrum means subjected to a suction draft, conveying said web of textilematerial on said perforated surface, said web being retained on saidperforated surface only by said suction draft, heating the textilematerial to a shrinking temperature by drawing a heated treatment mediumthrough the web of material while the web is being conveyed on theperforated surface, the differential pressure across the web of maTerialon said perforated surface being lower than about 40 mm. water columnwhich is less than the shrinkage forces acting on said web of textilematerial whereby a uniform shrinkage of the web of material is obtainedon said perforated surface, and further heating the web of shrunktextile material on a perforated surface of at least one other sievedrum means subjected to a suction draft to effect heat-setting of saidtextile material while said web is in a smoothed-out condition.
 2. Theprocess of claim 1, wherein the differential pressure at the web ofmaterial is lower than about 20mm water column.
 3. The process of claim1, comprising overfeeding the web of material to the surface of thefirst sieve drum longitudinally and laterally such that the width andthe length of said web of material is conveyed on said sieve drum in acorrugated state.
 4. The process of claim 1, wherein the continuousrandom web comprises at least one synthetic fiber type selected from thegroup consisting of polyvinyl chloride, polyvinyl alcohol andpolyacrylonitrile.
 5. The process of claim 1, wherein steam is blownagainst both sides of the web of material before the material is placedon the perforated surface of the sieve drum means through which saidtreatment medium is drawn to effect shrinkage of said material.
 6. Theprocess of claim 1, wherein the textile material consists of at leasttwo different types of fibers, one fiber type shrinking substantiallymore under the influence of heat than the other.
 7. The process of claim1, wherein the web of textile material is first penetrated by atreatment liquid with a temperature greater than about 90*C. to effectshrinkage of said material on said perforated surface of said at leastone sieve drum means and thereafter the web of material is heated by agaseous treatment medium to a higher temperature for drying and refixingof said material on the perforated surface of said at least one othersieve drum means.
 8. The process of claim 7, wherein the gaseoustreatment medium is heated to a temperature ranging from 140* to 220*C.9. The process of claim 7, wherein the web of material is sprayed withcold water before it is penetrated by the treatment liquid.
 10. Theprocess of claim 7, wherein the continuous random web comprises at leasttwo different fiber types selected from the group consisting ofpolypropylene and a polyamide, polypropylene and a rayon staple,polypropylene and a polyester, polyamide high-shrink fibers and normalpolyamide fibers, polyester high-shrink fibers and normal polyesterfibers.